Problem: Evaluate: $(723)(723)-(722)(724)$.
Explanation: Note that we have a difference of squares: $(722)(724) = (723 - 1)(723 + 1) = 723^2 - 1^2$. Thus, this expression evaluates to $(723)(723) - (722)(724) = 723^2 - (723^2 - 1^2) = 1^2 = \boxed{1}$.